Why are giant slabs of Arctic ice melting so fast? [ICESCAPE]

Don Perovich on the Ice. Click for full size. (Photo: Haley Smith Kingsland)

Dr. Kevin Arrigo is a Professor in the Department of Environmental Earth System Science at Stanford University. He is the Chief Scientist for NASA’s ICESCAPE (Impact of Climate change on the Eco-Systems and Chemistry of the Arctic Pacific Environment) mission this summer onboard US Coast Guard Cutter HEALY.

“This is the best ice floe ever,” remarked Don Perovich (Cold Regions Research and Engineering Laboratory), leader of ICESCAPE’s sea ice team. It looks like a normal floe to me, but to Don, each new floe he samples is the best floe ever. Ice floes are big slabs of frozen ocean, and the ice team is trying to understand why they are melting so fast and what the consequences for the Arctic marine ecosystem might be.

Although there are actually three research groups studying sea ice as part of ICESCAPE, including my own, Don’s group is especially interested in how much sunlight is absorbed and reflected by sea ice (you’ll read about the other groups in a later post). This is an important issue because the sea ice near the Earth’s two poles reflects a lot of the sun’s heat and helps keep the planet cool. What worries scientists is that as the sea ice melts, the ocean will absorb more heat, causing it to warm up and melt even more ice. A warmer Arctic Ocean means less sea ice and ultimately, a warmer planet.

His other team members include Bonnie Light, Ruzica Dadic (both from University of Washington), and Chris Polashenski (Dartmouth College). They are studying how melt ponds, ubiquitous little aquamarine lakes that sit on the surface of the sea ice, increase the amount of light energy the ice absorbs. In areas without melt ponds, the ice surface is usually very bright white, meaning that the ice is reflecting lots of light and absorbing very little. Where the ponds reside, however, the ice surface is much darker, especially when the ponds are deep, which is a sure sign that the ice is absorbing lots of light and heating up.

The team is using some sophisticated optical equipment to make detailed measurements of the amount of light absorbed by ice with and without melt ponds. They are also bringing numerous yard-long ice cores back home so they can study their crystal structure and other physical characteristics in greater detail. One big question they are trying to tackle is how these melt ponds form, grow, and eventually shrink and how this evolution alters the amount of light and heat that the ice absorbs.

Eventually, this new information can be plugged into the next generation of global climate models to produce better predictions of Arctic sea ice extent. Arctic sea ice is melting fast, and the more we understand why, the better chance we have to reverse this frightening trend.